An odor property of vanilla is very valuable in the flavor and/or fragrance industry. In order to impart this odor property to a flavor and/or fragrance composition or product, vanillin, ethyl vanillin or a combination of two of them is generally used, which has favorably been applied, for example, to fragrancing of fragrance products such as perfume, cologne and air freshener.
Recently, due to the growing needs of consumers, there are needs for fragrancing a huge variety of products such as laundry detergents, household detergents, shampoo, body soap, soap, toothpaste and hair styling agents with an odor property of vanilla.
Vanillin and ethyl vanillin, however, are known to induce deterioration of odor and unfavorable coloring, and susceptive to decomposition, alteration, discoloration or polymerization or the like under an alkaline condition, an oxygen-existing condition, a temperature condition or a light exposure condition or the like, as a result of which the vanilla-like odor used for odoring changes. This has been a problem where vanillin and ethyl vanillin cannot be used depending on the vehicle. Specifically, vanillin and ethyl vanillin are unstable in vehicles of soap, shampoo and alcoholic compositions. So when a fragrance composition containing vanillin, ethyl vanillin or a combination of two of them is used in such a vehicle, deterioration and brown discoloration of the odor will be caused within short time, and the vanilla odor property will vanish.
Under such circumstances, there has been a need for a development of a fragrance composition that has a vanilla odor property, and that is chemically stable even when blended in a product containing a vehicle of soap, shampoo or an alcoholic composition.
Until now, a number of techniques for preventing alteration and discoloration of vanillin have been proposed.
For example, a method in which an iodized salt is added to a chemical drug containing vanillin in order to prevent discoloration of vanillin (Patent Literature 1: Japanese Unexamined Patent Application (Translation of PCT) Publication No. 2010-526199) and a method in which an antioxidant such as butylated hydroxytoluene (BHT) is added in order to suppress deterioration of an aldehyde perfume chemical component containing vanillin (Patent Literature 2: Japanese Unexamined Patent Application Publication No. 2011-256392) have been proposed.
In addition, discoloration of a textile product due to contact with wood or cardboard during storage of the textile product is also considered to be caused by vanillin generated upon decomposition of lignin contained in wood or cardboard. As a technique for preventing this, methods have been proposed in which a textile is treated with a phosphate ester ammonium salt-type anion surfactant, a sulfate ester ammonium-type anion surfactant, a sulfonate ammonium-type anion surfactant or a fluorine-containing water-and-oil repellent to absorb vanillin that causes coloring (Patent Literature 3: Japanese Unexamined Patent Application Publication No. 2001-279576, Patent Literature 4: Japanese Unexamined Patent Application Publication No. 2001-89970 and Patent Literature 5: Japanese Unexamined Patent Application Publication No. Heisei 10-273878).
These methods, however, lack sustainability against alteration caused by vanillin. Moreover, there are cases where blending an additive is unacceptable depending on a product base. Furthermore, there is a problem that the textile fabricating techniques cannot be applied to flavors and/or fragrances.
In response to this, instead of using an additive, it has been proposed to derivatize vanillin itself to obtain a vanillin-like flavor and/or fragrance that is less likely to alter or discolor.
For example, compounds such as 4-formyl-2-methoxyphenyl 2-methylpropanoate (“ISOBUTAVAN”: manufactured by Givaudan) (see Patent Literature 6: specification of U.S. Pat. No. 4,473,588), 2-ethoxy-4-methylphenol (“Ultravanil”: manufactured by Givaudan) (see Patent Literature 7: Japanese Unexamined Patent Application Publication No. Showa 61-103819) and 2-ethoxy-4-(methoxymethyl)phenol (“METHYLDIANTILIS”: manufactured by Givaudan) (see Patent Literature 8: specification of U.S. Pat. No. 4,657,700) are used as alternatives to unstable vanillin or ethyl vanillin, primarily in combination with vanillin or ethyl vanillin.
However, each of them has characteristic shortcomings. For example, 4-formyl-2-methoxyphenyl 2-methylpropanoate is a compound in which the phenol group of vanillin has been esterified, which is susceptible to hydrolysis in a vehicle. Hydrolysis of this compound will free vanillin and generate isobutyric acid, which will result strong unpleasant fatty acid malodor. Although an o-alkoxy phenol such as 2-ethoxy-4-methylphenol is chemically stable, it has unpleasant phenol malodor in addition to a vanillin-like odor property. 2-Ethoxy-4-(methoxymethyl)phenol also lacks chemical stability and is very susceptible to coloring, and the odor property is not comparable to the odor quality and the strength of vanillin or ethyl vanillin. Therefore, it is difficult to use these compounds independently as an alternative compound for vanillin.
Japanese Unexamined Patent Application (Translation of PCT) Publication No. 2013-525535 (Patent Literature 9) describes alkyl aryl carbonates, such as 2-methoxy-p-cresol methyl carbonate, as compounds having a vanillin-like odor property. Although this compound is chemically stable, the vanillin-like odors trength is weak so it is difficult to be used independently as an alternative compound for vanillin.
Moreover, Motoichi INDO, “Synthetic Aromachemical: Chemicals and Product Knowledge, Expanded and Revised edition”, The Chemical Daily Co. Ltd., pages 146-147, expanded and revised edition published on Mar. 22, 2005 (Non-Patent Literature 2) describes 2-ethoxy-5-(1-propenyl)phenol (also known as “vanitrope”). Although this compound is chemically stable, its odor quality is less sweet compared to vanillin and has unpleasant phenol malodor, and thus is difficult to be used independently as an alternative compound for vanillin.
Meanwhile, Osamu OKUDA, “Comprehensive List of Flavor and/or Fragrance Chemicals [II]”, Hirokawa-Shoten Ltd., published on Jan. 15, 1968, page 680 (Non-Patent Literature 1) lists a variety of vanillyl alcohol derivatives such as vanillyl alcohol, ethylvanillyl alcohol, isovanillyl alcohol and veratryl alcohol. The document describes that these compounds can be used as a retaining agent or a raw material for synthesis of a flavor and/or fragrance but it does not describe the use of these compounds as odor components. In addition, it does not describe as to what kind of specific odor property these compounds have.
Steffen Arctander, “Perfume and Flavor Chemicals (Aroma Chemicals) II”, Allured Publishing Corporation, published in 1994, page 3073 (Non-Patent Literature 3) describes that vanillyl alcohol has a vanilla-like odor property. However, it describes that the odor strength of vanillyl alcohol is much lower compared to that of vanillin.